TS-440s VCO potting

This Kenwood TS-440s was reported to have PLL issues.  After doing some research it was discovered that the potting material in the VCO was prone to turn conductive after many years.  This throws off the VCO especially in humid environments.

The repair is relatively easy, but labor intensive.  The top cover is removed and the first board flips up out of the way.  The board underneath only has a few connectors and comes out of the case rather easily.

The can around the VCO is best removed to perform this repair.  A few quick turns with the desoldering tool and the can can be separated from the board.  The potting material adheres to the can, but a dental pick can be used to pull and pry and material away gently.  The adjustable transformer also had to be removed to get the potting material out from underneath it.

They say there is better life through chemistry and the proof is here.  The potting material residue on the can was the perfect test subject for what chemical would be best to dissolve it rather than trying to pick it out a little at a time.  It turns out that ordinary brake cleaner softened the potting material back to a jelly-like state, but did not hurt the components on the board.  Dark places around certain components lead me to believe that this was the more overheated and more conductive material.  It was harder to remove and took more scraping with the dental pick.

When all the potting material was removed, the can could be soldered back in, and the radio re-assembled.

A quick test with the SDR proved that the transceiver did not drift when connected to a dummy load.  An on-air QSO confirmed that the audio was good on TX, and listening to WWV confirmed that the alignment was good for RX.